The latest mass killing in the U.S. emerged Thursday when police investigating the deaths of a woman and her son in Duluth, Minnesota, discovered another woman and boy dead at a different home along with the man police suspected.
It is the country鈥檚 33nd mass killing this year, according to maintained by The Associated Press and USA Today in partnership with Northeastern University.
Duluth Police Chief Mike Ceynowa the first killings identified the woman's former partner as a suspect and went to his house, where they found him dead along with his wife and son. Police said the suspect apparently shot himself. Ceynowa said the man had a 鈥減attern of mental health issues.鈥�
At least 144 people have died this year in mass killings, which are defined as cases in which four or more people die within a 24-hour period, not including the killer 鈥� the same definition used by the FBI.
Last year ended with 217 deaths from 42 mass killings, making 2023 one of the deadliest on record.
Here is a look at other U.S. mass killings this year:
: Oct. 21
A 15-year-old boy was arrested after police found his parents and three of his siblings dead at a home in the rural community. The boy's 11-year-old sister, who survived the attack by playing dead, told police he used their father's handgun. She said he was the only one who knew the code to the lockbox where it was kept.
: Sept. 21
Four people were killed and more than a dozen injured outside a nightspot in what police described as a targeted 鈥渉it鈥� by multiple shooters. Police Chief Scott Thurmond said authorities believe the shooting targeted one of the people who was killed, possibly in a murder-for-hire. A vehicle pulled up and 鈥渕ultiple shooters鈥� got out and began firing, then fled, he said.
: Sept. 4
Two students and two teachers were killed at Apalachee High School northeast of Atlanta, and another teacher and eight other students were injured. A 14-year-old student has been charged as an adult with murder. Authorities also charged his father with involuntary manslaughter, second-degree murder and cruelty to children, saying he gave his son access to the rifle used in the shootings.
: Sept. 2
Four people sleeping on a Chicago-area train were fatally shot on Labor Day morning. Police were called to a Chicago Transit Authority station just outside the city. A 30-year-old man was arrested. The victims were a woman and three men. A motive wasn't immediately disclosed.
: Aug. 31
Four people were found dead after firefighters extinguished multiple blazes at a home in upstate New York, though authorities said they likely were killed by something else. Firefighters found the bodies of two adults, a 2-year-old boy and a 4-year-old girl.
: Aug. 25
Police said a man distraught that he was being forced to move from his late mother鈥檚 home shot and killed four family members before taking his own life. The shooting occurred three days after his mother's funeral.
: Aug. 24
Four males, ages 17 to 21, were shot to death at a park. A teenager was charged with murder in what police said was a robbery that turned violent. Multiple weapons were involved.
: July 31
Police said an intentional fire killed four people near Tampa. A 25-year-old man who lived in the house was charged with murder while engaged in arson. Three dogs also died.
: July 19
A grandmother, a mother and her two children, ages 5 and 4, were fatally stabbed at an apartment in Brooklyn. A 24-year-old man who knew the four was arrested.
: July 18
A man was charged with killing his wife and four children, ages 2 to 9, in a rural community in Bibb County. The man didn't say anything about a motive when taken into custody. 鈥淓ven seasoned officers told me it is the worst thing they鈥檝e ever seen,鈥� Sheriff Jody Wade said.
: July 13
The victims were shot at a nightclub. One man died on a sidewalk while two women were killed inside the club. Another man was pronounced dead at a hospital. Investigators believed some shots were fired from outside the club.
: July 10
Police arrested a man in the shootings of his wife, two children and his wife's parents in the San Francisco Bay area. The man's father-in-law went to a neighbor for help and spoke to police before he died.
: July 6
A birthday party turned deadly in the wee hours when four people were shot. The 21-year-old suspected gunman crashed his car in a ditch during a police chase and was found dead from a self-inflicted gunshot.
: June 24
A 48-year-old man barred from possessing guns because of a criminal record killed himself after fatally shooting five people, police said. The violence began after the man had an argument with a former girlfriend. The victims at the apartment complex included a neighbor who tried to help and the neighbor's mother and grandmother.
: June 21
A 44-year-old man shot people in the parking lot before shooting more inside the Mad Butcher grocery store, killing four. Police said he did not appear to have a connection to the victims. The shooting occurred in the middle of the day in Fordyce, about 65 miles (105 kilometers) south of Little Rock.
: June 12
A landlord was accused of killing a family of four and burning their bodies. The two children were ages 6 and 5. The family was reported missing by relatives. Police say a backyard fire pit was smoldering when they searched the property in Pasco County.
: June 5
Police said a metal pipe was used to kill four people in an outbuilding of a rural home near Cedar Rapids.
: April 29
Four officers were shot in the deadliest attack on U.S. law enforcement since 2016. They were killed when a task force of officers from different agencies tried to capture a 39-year-old man for illegally possessing a firearm and fleeing to elude in a different county.
: April 22
A 10-year-old boy awoke to find his parents and three brothers dead in their home near Oklahoma City, all fatally shot by his father, police said. Authorities believe the 42-year-old man killed his wife and three sons 鈥� ages 18, 14 and 12 鈥� then turned the gun on himself. Police said they did not immediately know why the fourth child was spared or have a motive for the shootings.
: March 27
A frenzied stabbing and beating rampage left four people dead in a matter of minutes and at least seven people injured. Authorities said a 22-year-old man was charged. Police didn't immediately know his motive. Rockford鈥檚 mayor said the victims were 63, 23, 49 and 15.
: March 11
The bodies of four people, ages 3 months to 90 years, were found inside the remains of a burning home. A fifth person with an apparent gunshot wound was discovered dead behind a chicken coop nearby, authorities said. A 45-year-old male suspect was found dead by suicide about 110 miles (180 kilometers) away, parked in a vehicle outside his relatives' home. Authorities did not immediately share details about a motive.
: March 10
Authorities said a woman and three children ages 10, 12 and 17 were fatally stabbed in a Manoa home. The woman's husband was also found dead. Police said a preliminary investigation shows the husband fatally stabbed his wife and children. Authorities did not immediately share a motive. Police said the five deaths mark the state's worst mass killing since 1999. They said there was no history of domestic calls to the residence.
: March 3
Police said three men with dark masks got out of a silver Kia and opened fire at an outdoor party in central California, killing three men and a woman and wounding seven others. The shooting happened on a street with modest homes facing a commercial district in King City, close to Pinnacles National Park.
: Feb. 19
Authorities said a 39-year-old woman intentionally set a fire at home to kill herself and her four children, ages 2, 5, 9 and 9. Investigators believe the mother set fire to a mattress, and left a note saying she intended to kill herself and her children, police said. Responding firefighters found the home engulfed in flames. Neighbors tried to save the family, but the fire was too intense.
: Feb. 16
Officials said four men were killed in a drive-by shooting. Dozens of shots were fired outside a Birmingham home, police said. People were standing outside a house as they got their cars washed when someone drove by and opened fire. No arrests were immediately reported.
: Feb. 11
Shootings over several hours left four people dead: a man in Bell, a man in a Los Angeles shopping center parking lot, a 14-year-old boy in Cudahy, and a homeless man in Huntington Park, authorities said. At least one other juvenile was wounded. Two suspected gang members were arrested in connection with the shootings, authorities said.
: Feb. 7
Six sets of human remains were recovered from the ashes of a fire that destroyed a home near Philadelphia, according to the county district attorney鈥檚 office. Authorities suspect those who died 鈥� including three children 鈥� were killed by a 43-year-old male relative who also died after shooting and wounding two police officers, the office said. A motive was not immediately identified.
: Jan. 23
Authorities found the bodies of six men in the Mojave Desert outside the sparsely populated community of El Mirage after someone called 911 and said he had been shot, according to sheriff鈥檚 officials. The men were likely shot to death in a dispute over marijuana, authorities said. The bodies were found about 50 miles (80 kilometers) northeast of Los Angeles in an area known for illegal cannabis operations. Five men were arrested and charged with murder.
: Jan. 21
Authorities said a 23-year-old man shot eight people 鈥� including seven of his relatives 鈥� and injuring a ninth person in a Chicago suburb. He fatally shot himself later during a confrontation with law enforcement in Texas. Authorities believe he was trying to reach Mexico. Police said the victims included his mother, siblings, aunt, uncle and two men he might not have known. They were found in two homes, outside an apartment building and on a residential street.
: Jan. 21
A 63-year-old man in suburban Chicago killed his wife and three adult daughters a domestic-related shooting, police said. The man allegedly shot the four family members 鈥� ages 53, 24 and two 25-year-old twins 鈥� after an argument at their home. He was charged with four counts of first-degree murder.
: Jan. 13
A 46-year-old man fatally shot his estranged wife and three other relatives, including his 8-year-old niece, at a home in suburban Houston before killing himself, authorities said. Authorities said the man had told his estranged wife that he wanted to reunite but she refused. In addition to killing his niece and estranged wife, he also killed her brother and sister, ages 43 and 46.
: Jan. 6
A 17-year-old boy was charged with killing four members of a neighboring family in central California. He lived next door to the victims 鈥� ages 81, 61, 44 and 43 鈥� in Reedley, a small town near Fresno. Three bodies were found in their backyard, including one buried in a shallow grave, while another was found in the detached garage of the teenager鈥檚 home, police said.
The Associated Press
