"Sometimes I remember that and I start to practice a little instead to forget," he said in Spanish.
January 23 marks one year since a mass shooting rocked the tight-knit community of Half Moon Bay.
A gunman killed seven farmworkers, including Pedro's brother, Jose, at two different farms.
Pedro survived but was hospitalized for two months.
VIDEO: Half Moon Bay community remembers, mourns 1 year after mass shooting
Half Moon Bay community remembers, mourns 1 year after mass shooting
Now, he's in a class that's helping farmworkers heal from the tragedy through music.
So is Yesenia Garcia.
"It helps a lot," she said. "I actually know a couple of people from other farms so that's why we were like, 'who is it,' and when we finally (found) out, we were all sad."
Musician and San Jose resident Hernan Hernandez teaches the accordion class, organized by the nonprofit ALAS.
The program is funded through a grant from the Silicon Valley Community Foundation.
Hernandez's dad is in the famous Mexican band, Los Tigres del Norte.
VIDEO: Benefit concert held for Half Moon Bay farmworkers navigating difficult year
Benefit concert held for Half Moon Bay farmworkers navigating difficult year
"Music has always been in our household," Hernandez said. "And so that was one of the things that he taught me at a young age, whatever you learn, whatever you take from this life, make sure you give it back, make sure you teach the next ones... So for me it's really important that I give back."
Hilario Lopez lived at one of the farms that turned into a crime scene. His wife and young son were there during the shooting.
"I was worried because it was very dangerous for them," Lopez said in Spanish.
In December, the group played for the community.
"We felt good," Lopez said. "It was the first time I'd been on a stage. It was very beautiful."
Especially after everything they've been through.
The mass shooting shed light on the deplorable living conditions of farmworkers and their other struggles, such as low pay.
VIDEO: Grieving families of Half Moon Bay shooting victims prepare to bring loved ones home to Mexico
Grieving families of Half Moon Bay shooting victims prepare to bring loved ones home to Mexico
With each note he plays, Pedro gets closer to finding some peace again.
And as the first anniversary of the tragedy arrives, he hopes his brother and other farmworkers aren't forgotten.
"It's tough," Romero Perez said. "I always remember him. I don't know why that happened, why to us."
Half Moon Bay has established a committee to create a permanent memorial to honor the farmworkers who died, such as through a statue or garden. Nothing has been determined yet.
There was a remembrance ceremony organized by Half Moon Bay at the Boys and Girls Club on Sunday and an event planned by ALAS on Tuesday.