Yesterday a computer specialist named Mickaël Harpon attacked and killed four people inside police headquarters in Paris. A ceramic knife was used in the attack and police are still trying to verify whether he brought it with him or had it stashed somewhere inside. One other person was seriously wounded in the attack but survived. A rookie police officer confronted Harpon and when he wouldn’t drop the knife, shot and killed him.

When the story broke, police suggested the attack may have been the result of a dispute with superiors. Things changed Friday morning when a police spokesperson said that all motives were still being considered. Friday afternoon, police released a brief statement that said anti-terrorism prosecutors had been put in charge of the investigation.

The office announced the decision in a two-line statement and provided no details about the evidence that persuaded prosecutors a terror investigation was warranted.

David Le Bars, head of the Union of National Police Commissioners, told French broadcaster BFM TV it came from easily accessible sources found in a search of the attacker’s home.

“We knew that searching through his computer histories, the websites visited, his relations, we would quickly have some information,” Le Bars said…

Authorities said the attacker had worked for the Paris police force since 2003, didn’t have a history of psychiatric problems, and converted to Islam 18 months ago.

Whatever information the police have gathered from the search of the attacker’s computer and phone, they haven’t shared it yet. In previous terror attacks, the attacker often announces his motive during the attack, i.e. by shouting “Allahu Akbar.” However, the Guardian reports there are no witnesses left to what happened when the attack began:

There were no surviving witnesses from the room where he first attacked and killed three officers, so it is not clear what he may have said to them before the attack.

The BBC does have one interesting detail that I don’t see being reported anywhere else:

He converted to Islam 18 months ago, according to reports, and had recently stopped talking to female colleagues in the office. But a government spokeswoman said on Friday morning that there was no indication he had been radicalised before the attack.

That seems odd and also contradicts public statements that no one had noticed any changes in his behavior. We’ll have to wait for more information to know definitively what happened here, but for the moment it’s looking possible this was a terror attack.

Update: It was definitely terrorism.

The attacker had contacts with people suspected of belonging to the ultraconservative Salafist movement of Islam, the prosecutor said.

The attacker had expressed his support for the 2015 Charlie Hebdo attacks, Ricard said, and “certain acts committed in the name of this religion,” as well as a desire to “cease certain forms of contact with women” and his adoption of traditional Muslim clothing “in the last few months.”

So how were police so far off the mark at first? CNN doesn’t say but earlier reports noted the attacker’s wife told police that he was having a mental problem. But it appears now that she knew that was a lie:

The attacker and his wife exchanged 33 text messages over 29 minutes the morning preceding the attack, and their content was “exclusively religious,” the prosecutor said.

The last exchange ended with “Allahu akbar,” which means “God is greater” in Arabic, and “follow the vision of our prophet Mohammed and meditate over the Quran.”

The attacker bought two knives used in the attack shortly after this conversation.