Former Van Halen bassist Michael Anthony is honoring the short life of his infant grandson by joining an upcoming fundraising walk for Children’s Hospital Los Angeles.

Michael shared the news of his devastating personal loss on Facebook, posting an update informing fans that his grandson Rex had died at just 15 days old. Diagnosed with heart disease shortly after his birth, Rex underwent open heart surgery to correct his condition, but doctors soon realized he was too weak to recover from the procedure.

In honor of those efforts — and Rex’s too-brief time on Earth — Anthony has joined this year’s Walk L.A. fundraiser, scheduled for June 17 at Griffith Park in Los Angeles. Noting that the non-profit organization is “the only hospital solely dedicated to the health of children in Los Angeles,” Anthony’s seeking to raise $3,450 for his Walk L.A. team, dubbed Rex and the Heart Beaters.

Anthony is also inviting fans to start their own Walk L.A. fundraising pages and take part in the event, which takes participants on a 4-km loop through the park. For more information, visit the Walk L.A. website.

Our heart and prayers are with your Michael Anthony!