Eight people were also injured in the attack, which police believe was a “targeted act of violence”.
It shocked the local community and church nationwide.
Money has also been donated to fundraisers for victims and their families. Flags were lowered throughout Michigan to honour the victims, and neighbours, including members of other denominations, have held vigils.
One survivor of the attack wrote in a letter that she had forgiven the gunman for killing her father.
“When he [the gunman] came over to me I felt very calm, peaceful even as I kneeled next to my dad, my hands still on dad,” the woman wrote in the letter, shared with BBC’s US partner CBS News. Her name was not published to protect the family’s privacy.
“I never took my eyes off his eyes, something happened, I saw pain, he felt lost. I deeply felt it with every fiber of my being,” she wrote.
“I forgave him, I forgave him right there, not in words, but with my heart.”
Investigators said earlier this week that they are still searching for a motive behind the attack, which happened during a Sunday service attended by hundreds of people.
Officials have said Sanford, 40, was a former Marine who was once deployed to Iraq. In an old interview with local outlet Clarkston News, Sanford said that he was a sergeant and served in Fallujah in 2007.
He had previous arrests for burglary and operating a vehicle while intoxicated, officials said on Monday. Sanford is from a suburb of Flint of about 30,000 people, just a few miles away from Grand Blanc Township.