"My heart dropped -- it literally fell through the floor," said Jessica Weiss, friend of shooting victim.
Weiss, a senior at Lowell High School in San Francisco, is struggling with the loss. She worked as a lifeguard alongside 20-year-old Justin Valdez and they became fast friends.
"He has this infectious personality. He was always that person you could look to make you smile," said Weiss.
Valdez was shot and killed as he got off a street car at Randolph and Bright Streets Monday night. Nikhom Thephakaysone, 30, was arrested on suspicion of murder outside his home on Tuesday. Investigators had been circulating surveillance video from Muni. They say it helped lead them to the suspect. Police believe the killing was random and unprovoked. Which only makes it harder on people knew Valdez, like his high school principal, in Southern California.
"For somebody who lived his life as one of the strongest role models on campus, to be killed this senselessly doesn't make any sense to anybody," said Principal Steve Osburn.
Police said they also found $20,000 in cash and other survivalist gear at Thephakaysone's home. It turns out he is also a San Francisco State student. Police added they believe he confronted other people before getting on Muni Monday and police said he pulled a gun on at least one other person.
By all accounts, Valdez was a natural leader -- with big plans.
"He talked about changing the world; he talked about saving the planet. That's just really inspirational to hear now-a-days," said Weiss.
Valdez's family and friends gathered at San Francisco State Thursday night for a candlelight vigil. A witness to the crime came to pay her respects.
Anyone with information about the case is asked to call the Police Department's homicide detail at (415) 553-1145. People can also call anonymously to (415) 575-4444 or send a tip by text message to TIP411 with "SFPD" in the message.