The city of San Bernardino, California, planned to hold a public ceremony Friday night to remember victims of an attack that occurred a year ago, though some questions about the attack have yet to be answered.
On December 2, 2015, Syed Rizwan Farook and his wife, Tashfeen Malik, walked into the Inland Regional Center, where Farook worked, and fired more than 100 rounds at his co-workers, killing 14 of them and wounding 22, a U.S. Justice Department report said.
The couple were killed about four hours later in a shootout with police, but questions about their motive remain.
The FBI began investigating the shooting as an act of terrorism after it found an online post made by Malik pledging allegiance to the Islamic State, but authorities said there was no direct link between the couple and the jihadist group.
This week in an interview with ABC News, San Bernardino Police Chief Jarrod Burguan said the FBI discovered emails between Malik and Farook that led police to believe they carried out the attack because a holiday party was set to take place in the building later that day.
According to Burguan, Malik said in the emails "she didn't think that a Muslim should have to participate in a non-Muslim holiday or event."
"That really is one of the very, very few pieces of potential evidence that we have that we can truly point to and say, 'That possibly is a motive in this case,' " he said.
Officials said they still didn't know for sure why the couple targeted the IRC. Burguan said the best they could do was "theorize."
"There are a lot of questions, and we don't have all the answers," he said Thursday. "We never established the motive."
Police planned a 14-mile memorial bike ride Friday, which was set to end at the shooting site. At that time, they are to hold a short memorial service for those who were killed.
Earlier Friday, San Bernardino County employees observed a moment of silence at 10:58 a.m. to mark the moment police received the first 911 call after the shooting started.