Oct. 31 (UPI) -- Mail bomber suspect Cesar Sayoc had planned a "domestic terror attack" as far back as July, federal prosecutors say in newly-filed court documents.
In a letter to District Judge Edwin Torres, prosecutors from the U.S. Attorney's Office said the homemade pipe bomb devices mailed last week to 15 prominent Democrats and critics of President Donald Trump contained shards of glass that "could only have been intended to maximize harm."
The letter urges Torres to keep Sayoc in jail as he awaits trial, citing security concerns.
"The evidence of the defendant's terror campaign is still being collected but is already overwhelming," the letter states. "Because of the powerful proof that the defendant perpetrated these acts, he poses a substantial danger to the community.
"In light of the consequences at issue and the likelihood of conviction, the defendant is also a substantial flight risk."
Sayoc faces at least five federal charges in New York City. His next hearing is set for Friday.
Prosecutors said in the request Sayoc's laptop computer -- which was found inside his van, which was covered in pro-Trump and anti-Democrat imagery -- has been searched, as has his cellphone.
On the computer, they added, a file titled "Debbie" was found to be created in July. Officials believe it might refer to Florida Rep. Debbie Wasserman Schultz, who's Sunrise, Fla., office was used as the return address for the pipe bombs.
The laptop also showed Sayoc had searched the Internet for addresses of former Vice President Joe Biden, billionaire George Soros, Hillary Clinton, former National Intelligence Director James Clapper and former U.S. Attorney General Eric Holder. All five received pipe bomb-like devices in the mail last week.
In each case, the phrase "and family" or "wife and kids" was added to the Internet search.
Prosecutors said Sayoc's cellphone contained photographs of several homes belonging to persons on the target list.
Sayoc was arrested Friday after most of the mailed pipe bombs were discovered. Another bomb addressed to CNN's Atlanta headquarters was found Monday. None of the bombs exploded.