Former Beatle Sir Paul McCartney has been seen on the March for our Lives against gun violence in New York.
"One of my best friends was killed in gun violence right around here," Sir Paul told CNN, "so it's important to me."
Sir Paul's bandmate John Lennon was shot in the back five times outside his New York apartment on December 8, 1980. He died on the way to hospital.
McCartney was wearing a shirt that read "we can end gun violence".
"I don't know" if we can end gun violence, Sir Paul told CNN, "but this is what we can do, so I'm here to do it."
Mark David Chapman, the deranged fan who killed Lennon, remains in jail. He has been up for parole several times, without success.
Drummer in the Beatles, Ringo Starr, was knighted earlier this week.
Hundreds of thousands of people attended March for our Lives events across the US, led by survivors of the Parkland shooting in February.
"You can hear the people in power shaking," survivor David Hogg told the crowd in Washington, to loud applause.
"We're going to make sure the best people get in our elections to run not as politicians, but as Americans. Because this is not cutting it," he said, pointing at the Capitol building. "We can and we will change the world."
In a message to the students on its TV network, the pro-gun National Rifle Association said "no one would know your names" if more people on school campuses were armed.
The NRA accused the children of "getting ready to use your First Amendment to attack everyone else's Second Amendment", referencing the US constitutional rights to free speech and being armed.