F.B.I. agents arrived late Monday night at the Houston home of an 18-year-old arrested on terrorism charges.

The investigators knocked on the family's door around 8:30 p.m. Monday, went inside and stayed about an hour.

"The boys are sharp, both of them are, he's the most laid back one," said Edward Hood, their next-door neighbor.

Hood saw no signs of the troubled teen described in federal court documents.

"When they were able to go to college, they were 14 or something like that, they were too young to go, they had to wait a year or so before they could get in," Hood said.

Friday, F.B.I. agents arrested Kaan Sercan Damlarkaya. Court documents say the man, who was born in Houston, lives with his parents and older brother. He's accused of distributing explosive-making instructions and trying to provide material to ISIS.

No one answered the door at his family's address on Nova Drive off Briar Forest.

"Kind of surprised," said Johnathan Scott, another neighbor.

Scott met the family after Harvey.

"When I came back the neighborhood was still flooded and I kinda rafted over and they was hanging out and I had a conversation with them," Scott said.

Nothing he says stood out, but to federal investigators a lot did. They say it goes back to at least 2014 and said Damalarkaya explained that it was his "dream" to be a martyr and have the biggest explosion.

"It's kind of shocking to hear a teenage boy would want to harm other people like that, but it's a sign of the times," Scott said.

According to court documents, Damlarkaya allegedly shared intentions to travel overseas to fight for ISIS or to commit an attack in the United States if he were unable to travel. Documents also state Damlarkaya asked if he could provide a farewell video to be broadcast if he died after following through with an attack.

According to the criminal complaint, Damlarkaya gave instructions on how to build an AK-47 or AR-15 assault rifle from readily available parts to avoid detection from officials.

Documents state Damlarkaya gave a formula to alleged ISIS supporters for the explosive, Triacetone Triperoxide (TATP), and instructions on how to use it in a pressure cooker device that contained shrapnel. He also talking about using a machete or Samurai sword as an alternative and claimed to carry a knife in case he was stopped by authorities, according to the complaint. Damlarkaya also said he slept with a machete under his pillow in case his house was ever raided, according to court documents.

In November, according to court documents, Damlarkaya said, “if I buy a gun or supplies for a bomb, they (presumably law enforcement) will heat up pressure (j)ust like a few months ago when I was trying an operation but they found out.”

The criminal complaint also alleges Damlarkaya claims he tried to get to Syria on two other occasions but failed.

Damlarkaya faces up to 20 years in prison if convicted.