Alexander Jackson, a 20-year-old University of Iowa student, called police Tuesday morning in a panic, claiming a masked intruder had shot him and his father inside their home.

When Cedar Rapid officers arrived at the scene, they found Jackson’s parents and his 19-year-old sister—a high-achieving student who introduced then-presidential candidate Andrew Yang during his 2019 visit to Iowa—fatally shot in different rooms of the expansive house. Jackson had suffered a gunshot wound to the foot after what he insisted was a struggle over the rifle with the mysterious man.

Police, however, now believe it was actually Jackson who murdered his father, 61-year-old Jan Jackson, his 68-year-old mother, Melissa Jackson, and their daughter, Sabrina. Jackson has been charged with three counts of first-degree murder and is being held in Linn County Jail on a $3 million bond.

While authorities have not yet established a motive, a criminal complaint obtained by The Daily Beast said that Jackson admitted that “his father had recently advised that he needed to find a job or move out.” It noted that the house showed no signs of being burglarized.

“This was a horrendous murder,” Assistant Linn County Attorney Ryan Decker said during Jackson’s initial court appearance on Wednesday. “This was more than just a murder, it was an execution of the defendant’s mother, father, and sister. Furthermore, the defendant’s concocted story of a phantom burglar shows the defendant acted out of malice and calculated intent to get away with these murders.”

According to the complaint, officers arrived at the scene at around 8:23 a.m. Tuesday after Jackson’s frantic call about a male intruder. Officers, however, instead found his three slain family members. They recovered a .22 caliber semi-automatic rifle believed to be the murder weapon.

Jackson told authorities that he “woke up to the sound of gunfire and was shot in the foot during a struggle with a masked man over the rifle,” the complaint states. He told police he and his father had cleaned the rifle the night before and left it on the fireplace overnight.

The incident sent shockwaves through the Jackson family’s quiet suburban community. A candlelight vigil has been planned for Wednesday night at Kennedy High School, which Jackson and his sister attended before they both went to the University of Iowa.

In 2019, Sabrina made local headlines when she introduced Yang—who is now running for New York City mayor—during his discussion with state Sen. Rob Hogg about climate change. According to IowaStartingLine, the then-senior described how she first heard about Yang on a podcast and was immediately enthralled.

“Yang’s political outlook is a breath of fresh air,” Sabrina Jackson said during her introduction speech. “Yang isn’t interested in the rhetoric of one side of the argument, but he listens to everybody with respect. He’s an outsider to politics, sure, but he’s the right kind of outsider. He’s experienced with the economy and the business of our country.”

A year later, she would follow her brother to college about 35 miles away from home, where she studied at the College of Liberal Arts.

Alexander Jackson, who graduated high school in 2019 where he played the flute in the school’s symphony band, attended the same college, according to the Associated Press. In a statement to The Daily Beast, a university spokesperson said “our thoughts are with those impacted by this tragic situation.”

The Daily Beast could not find any prior criminal history for Jackson or any of his family members in Iowa. On Wednesday, police said that he was put on suicide watch, but noted that the practice is standard for new inmates facing a possible life sentence for their accused crimes.

Jackson’s next expected court hearing is on June 25.