BOSTON — Just hours before one of the Boston Marathon suspects and his brother allegedly gunned down a campus police officer, authorities say he exchanged a series of text messages with a friend who’d become suspicious after seeing what looked like a familiar face being flashed on television.

Dias Kadyrbayev, a student at the University of Massachusetts Dartmouth, texted his college buddy Dzhokhar Tsarnaev, saying he looked like one of the bombing suspects.

“Tsarnaev’s return texts contained ‘lol’ and other things Kadyrbayev interpreted as jokes such as ‘you better not text me’ and ‘come to my room and take whatever you want,”’ an FBI agent wrote in an affidavit.

Those texts set off a series of events that on Wednesday led to Kadyrbayev and his roommate Azamat Tazhayakov, natives of Kazakhstan, being charged with conspiring to destroy emptied fireworks and other evidence linking their friend to the deadly April 15 blasts. Robel Phillipos, who graduated from Cambridge Rindge and Latin High School with Tsarnaev in 2011, was charged with lying to investigators about the April 18 visit to his friend’s dorm room to retrieve the items.

Tazhayakov also told authorities that during a meal about a month before the terror attacks, Tsarnaev informed him and Kadyrbayev “that he knew how to make a bomb.” That is significant because, before he was advised of his rights not to speak with authorities, the 19-year-old bombing suspect allegedly said his older brother had only recently recruited him to be part of the attack.

Three people were killed and more than 260 wounded on April 15 when two bombs exploded near the marathon’s finish line. Tamerlan Tsarnaev, 26, died after a gunfight with police days later. Younger brother Dzhokhar was captured and remains in a prison hospital.

According to the FBI account, just hours after surveillance camera photographs of the two suspects were flashed around the world April 18, Tsarnaev’s friends suspected he was one of the bombers and removed the backpack along with a laptop from Tsarnaev’s room at UMass Dartmouth.

One of them later threw the backpack in the garbage, and it wound up in a landfill, where it was discovered by law enforcement officers last week, authorities said. In the backpack were fireworks that had been emptied of their gunpowder.

Investigators have not said whether the pressure cooker bombs used in the attacks were made with gunpowder extracted from fireworks.

The lawyers for the Kazakh students said their clients had nothing to do with the bombing and were just as shocked by the crime as everyone else. Phillipos’ attorney, Derege Demissie, said outside court: “The only allegation is he made a misrepresentation.”

The Kazakh students did not request bail at a court hearing and will be held for another hearing May 14. Phillipos was held for a hearing on Monday. If convicted, Kadyrbayev and Tazhayakov could get up to five years in prison and a $250,000 fine. Phillipos faces a maximum of eight years behind bars and a $250,000 fine.