The fourth anniversary of the deadly Boston Marathon attacks was marked on Saturday with One Boston Day — a day of volunteering and random acts of kindness.

Quiet remembrances were planned throughout the day to remember the victims who were killed when two bombs planted near the finish line exploded on April 15, 2013. The families of Martin Richard, 8, Lingzi Lu, 23, and Krystle Campbell, 29, took part in separate wreath laying ceremonies on Boylston Street at the sites where the bombs went off. Massachusetts Governor Charlie Baker along with Boston Mayor Marty Walsh joined survivors of the attack as the wreaths were laid.

More than 260 people were wounded when the bombs exploded and sprayed shrapnel into the crowds.

Sean Collier, 26, a Massachusetts Institute of Technology police officer also was killed days later while struggling with the bombers as they tried to steal his gun. His family members also attended the wreath ceremony.

A bell ringing ceremony then took place at Old South Church, marking the times of the tragedy. The ceremony began at 2:49 p.m., the same time the bombs went off.

For their acts of kindness, residents in Dorchester partnered with the Martin Richard Foundation to clean up the neighborhood. Others donated blood in Watertown and at the Sheraton Hotel in Boston. Others participated by bringing in sock donations to the Franklin Park Zoo.