THIS is quite significant:
"Investigators believe Archer traveled to Saudi Arabia in 2011 and to Egypt in 2012, FBI special agent Eric Ruona said, and the purpose of that travel was being investigated by the FBI."
I've seen a theme too, where the perpetrator is "not the most radical" yet carries out a undeniably radical act out in the name of Islam. I'm sorry to break some hearts here, but it is looking increasingly possible that he was a Muslim.
The likelihood of him attending a mosque is extremely likely. As the Imam of the Masjid Mujahideen said as per
this video that it is "plausible" that Archer did come there to pray, though he didn't recognize his name or likeness. However, the language is pretty vague.
Note that I am not linking anyone else in that mosque, the mosque itself, or the rest of Islam for that matter, to what Archer did.
So, is anyone else going to continue sitting here and keep denying this?