The sequence of events is grim but familiar in cities across the United States. A mass shooting takes place. A public vigil is held. A community comes together with an outpouring of anger, sadness and solidarity.

But for families of those killed in last weekend’s mass shooting in Springfield, Mo., in which an attacker fatally shot four people, what was already a tragic situation has been compounded by the coronavirus. The families will mostly be grieving in solitude.

Cierrah Hicks-Morris, whose brother, Matthew, was killed in the attack, is still in shock. She told a friend on Friday she was going into isolation and just wanted to scream.

Mr. Hicks-Morris, 22, was killed Sunday night during a late-night run to a gas station. According to Anice Farmer, a close friend, he whispered over the phone to his girlfriend that a shooter had entered the shop. His girlfriend heard gunshots, and the phone line cut.