Only days after the deadliest school shooting in Georgia’s history, the 14-year-old suspect is expected to make his first court appearance on Friday on four charges of felony murder.

In a community now awash in grief and shock, questions have swirled about what could have motivated the teenager to open fire at Apalachee High School in Winder, Ga., on Wednesday morning.

The youth, who was a student at the school, is accused of killing two students and two teachers. On Thursday, his father was also arrested and charged with second-degree murder and other crimes in connection with the shooting.

Officials say that a “complex investigation” is ongoing, and that they may file additional charges.

Here is what we know.

Shortly after 10 a.m. Wednesday, and barely a month into the new school year, gunfire erupted on the campus of Apalachee High School, which is roughly 50 miles from downtown Atlanta.

The shooter used a black AR-15-style semiautomatic rifle, according to arrest warrants. The four killings happened within minutes.