Hundreds of people have gathered at a candlelight vigil in Nashville, Tennessee to mourn the three children and three adults who were killed in a shooting at a Christian school this week.

The ceremony on Wednesday for the victims of the shooting at The Covenant School was largely sombre and silent, and filled with young people.

First lady Jill Biden and singer Sheryl Crow were among those attending, as were civic leaders including the mayor and police chief.

“Just two days ago was our city’s worst day,” Mayor John Cooper said.

“I so wish we weren’t here, but we need to be here.”

Earlier in the day, Pope Francis sent condolences to the city and offered prayers to those affected.

Crow has pushed for stricter gun-control laws and released a tribute song to the 20 children and six adults who were killed in 2012 at a primary school in Newtown, Connecticut.

She responded to a tweet from Republican Senator Marsha Blackburn of Tennessee in which Blackburn said she and her husband were “heartbroken” over the shooting and that she and her office stood “ready to assist”.

“If you are ready to assist,” Crow tweeted, “please pass sensible gun laws so that the children of Tennessee and America at large might attend school without risk of being gunned down.”

A 28-year-old former student drove up to the school on Monday morning, shot out the glass doors, entered and began firing indiscriminately.

Authorities have not yet determined the shooter’s motive but say the assailant did not target specific victims.

Police said the shooter, identified as Audrey Hale, was under a doctor’s care for an undisclosed emotional disorder and was not on the radar of police before the attack. Hale was fatally shot by police at the school.

Authorities have given unclear information on Hale’s gender.

For hours Monday, police identified the shooter as a woman. Later in the day, the police chief said Hale was transgender. In an email Tuesday, a police spokesperson said Hale “was assigned female at birth” but used masculine pronouns on a social media profile.