CHARLESTON, S.C. — President Barack Obama sang a hymn of hope and spoke with the fervor of a preacher as he eulogized a pastor and eight parishioners gunned down at a historic black church in an apparent hate crime — and he minced no words in calling for an end to racial injustice and gun violence in the United States.

In his eulogy for the Rev. Clementa Pinckney, Obama suddenly began singing “Amazing Grace,” quickly joined by ministers and some of the thousands who packed into the arena at the College of Charleston in South Carolina.

The nation’s first black president called for gun control and efforts to eliminate poverty and job discrimination, and said the Confederate battle flag — long a symbol of Southern pride — must be removed from places of honor.

“For many — black and white — that flag was a reminder of systemic oppression and racial subjugation. We see that now,” he said.

The president came to eulogize the Rev. Clementa Pinckney, a state senator and pastor of Emanuel African Methodist Episcopal Church in Charleston, a church founded by the leader of a failed slave revolt and burned to the ground by angry whites in 1822. After the Civil War, the church led efforts to expand equal rights in the South, hosting Martin Luther King Jr. during campaigns in South Carolina.