BOSTON — A Massachusetts Institute of Technology graduate student says he saw Boston Marathon bomber Dzhokhar Tsarnaev lean into the police cruiser of an MIT officer who was fatally shot after the bombings.

Nathan Harman testified Wednesday that he was riding his bike through an MIT courtyard when he saw a parked police cruiser. The driver’s-side door was open and there was someone leaning in.

Harman pointed to Tsarnaev in the courtroom, saying he was the man he saw.

Prosecutors say Tsarnaev and his older brother, Tamerlan, killed MIT police Officer Sean Collier in a failed attempt to steal his gun. The shooting came hours after the FBI released images of the brothers as suspects in the marathon bombings.

Tsarnaev’s lawyer previously told the jury he participated in the bombings but said Tamerlan was the mastermind. She said Tamerlan is the one who shot Collier.