On the evening of May 21, 1961, more than 1,000 Black residents and civil rights leaders including Dr. Martin Luther King Jr. and the Rev. Fred Shuttlesworth attended a service at Montgomery's First Baptist Church. The service, organized by the Rev. Ralph Abernathy, was planned to support an interracial group of civil rights activists known as the Freedom Riders. As the service took place, a white mob surrounded the church and vandalized parked cars.

The Freedom Riders began riding interstate buses in 1961 to test Supreme Court decisions that prohibited discrimination in interstate passenger travel. Their efforts were unpopular with white Southerners who supported continued segregation, and they faced violent attacks in several places along their journey. The day before the Montgomery church service, the Riders had arrived in Montgomery and faced a brutal attack at the hands of hundreds of white people armed with bats, hammers, and pipes. The May 21 service was planned by the local Black community to express support and solidarity. 

As the surrounding mob grew larger and more violent, Dr. King called U.S. Attorney General Robert F. Kennedy from the church's basement and requested help. Kennedy sent U.S. Marshals to dispel the riot; the growing mob pelted them with bricks and bottles, and the marshals responded with tear gas.

When police arrived to assist the marshals, the mob broke into smaller groups and overturned cars, attacked Black homes with bullets and firebombs, and assaulted Black people in the streets. Alabama Governor John Patterson declared martial law in Montgomery and ordered National Guard troops to restore order. Authorities arrested 17 white rioters and, by midnight, the streets were calm enough for those in the church to leave.

Three days later, troops escorted the Freedom Riders as they departed to Jackson, Mississippi, where they would face further resistance.