PELHAM, N.H. (WHDH) -- Graffiti farewell messages spray painted on a New Hampshire high school are now part of a criminal investigation.

As a tribute to 16-year-old Zach Andrews who died unexpectedly last weekend from complications with pneumonia, messages of "RIP" and "We Love You" were spray painted on Pelham High.

“He always made everyone smile, he made everyone’s day if they were down,” said Dylan Sylvester, a student.

Students say the memorial went up hours after word spread of Andrews’

Although the graffiti messages were out of respect, police say whoever did it crossed a line.

“What they have to understand is that it’s okay to memorialize your friend but you have to do it in a way where you're not damaging school property or town property,” said Lt. Brian McCarthy, Pelham, New Hampshire Police Department.

The messages are now part of a criminal investigation. Police are hoping surveillance cameras may have caught the spray painters in action.

“It’s a good thought, but they don’t need graffiti at school I guess,” said Nick Wolfrum, a student.

Police told 7News they have interviewed several students.