NESCONSET, N.Y. (CBSNewYork) — Friends, family and classmates bid a final farewell Monday to a Long Island teenager struck killed by a New York City subway train.

Liam Armstrong died last week on his 18th birthday.

Armstrong and his two friends were waiting for a train at the 79th Street station when they realized they were on the wrong platform, police said. Instead of taking the stairs, police said they attempted to run across the four tracks to get to the downtown platform.

Armstrong was struck and killed by a Bronx-bound No. 2 express train.

Armstrong was a senior at Smithtown High School East and a popular member of the lacrosse team.

A funeral Mass was held Monday morning at Holy Cross Church in Nesconset.

Susan Walsh’s son was Liam’s best friend and was with him the night he was killed. “Liam, he was an awesome funny kid,” Walsh told CBS 2’s Carolyn Gusoff. “I hope he is not remembered for this but for all the other beautiful things he did.”

Mourners hug at Liam Armstrong's funeral (CBS 2)

Mourners hug at Liam Armstrong’s funeral (CBS 2)

Liam’s father Chris  is a commanding officer in the Nassau Police Department and a longtime member of the pipe and drum corp, having played himself at countless funerals.

With tears in their eyes, colleagues did the honor for him, Gusoff reported.

Liam had recently enlisted in the Marine Corp, following his father into public service.

His Lacrosse teammates, wearing memorial bracelets, listened  intently to a homily directed to young ears.

The message, said Bishop John Dunne, is to never forget Liam by treating life with respect.

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