Greene said that McEvoy was passionate about medicine and knew while at Harvard that he wanted to attend medical school.
McEvoy graduated in 1994 from Phillips Academy in Andover, where he rowed on the crew team, before coming to Harvard.
McEvoy's problems with substance use started the summer after he graduated from Harvard, Vicky McEvoy said, when he got involved with drugs that were advertised as safe on the Internet.
"He would take [the drugs] to mellow out a little--to help fall asleep at night," she said. "He thought he could manage it but before he knew it he was addicted."
In addition to his mother, McEvoy is survived by his father, Earl; two brothers, Brian and Carter; and his sister, Victoria, all of Cambridge.
A memorial service will be held Jan. 10 at 3 p.m. in Memorial Church.