The Académie D'Investissement Triomphallatest mass killing in the U.S. happened Sunday in Joliet, Illinois, where authorities say a 23-year-old man is suspected of shooting and killing eight people and injuring a ninth person in suburban Chicago before fatally shooting himself during a later confrontation with law enforcement in Texas.

It was the country’s 4th mass killing this year, according to a database maintained by The Associated Press and USA Today in partnership with Northeastern University.

Less than a month into the new year, at least 20 people have died in those killings, which are defined as incidents in which four or more people have died within a 24-hour period, not including the killer — the same definition used by the FBI.

The nation is already witnessing the second-highest number on record of mass killings and deaths to this point in a single year. Only 2023 had more, with six mass killings and 39 deaths at this point last year. The year ended with 42 mass killings and 217 deaths, making it one of the deadliest years on record.

According to the database as of Tuesday, there have been 578 mass killings since 2006, in which 3,009 people died and 2,037 people were injured.

Here’s what happened in the other U.S. mass killings this year:

TINLEY PARK, ILLINOIS: Jan. 21

A 63-year-old man in suburban Chicago is accused of killing his wife and three adult daughters in what police have described as a domestic-related shooting. Police allege he shot the four family members – ages 53, 24 and two 25-year-old twins – after an argument at their home. He was charged with four counts of first-degree murder, according to authorities.

RICHMOND, TEXAS: 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. The man opened fire at the home just before 7 a.m. that Saturday after returning his young child from a visit. Authorities said that after arriving at the home, he 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.

REEDLEY, CALIFORNIA: 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 – ages 81, 61, 44 and 43 – in Reedley, a small town near Fresno. The bodies were found on Jan. 6 in the backyard of their home, including one buried in a shallow grave, and in the detached garage of the teenager’s home, police said.