EL PASO — Just about every morning for the past two weeks, Antonio Basco has risen before dawn to buy as many floral bouquets as he can fit in his car and carried them to a makeshift memorial for the victims of the mass shooting in El Paso.

He places the flowers one by one around the white wooden cross for Margie Reckard, his wife. This is his solemn ritual, born of grief and unmooring: tending Margie’s garden.

“She loved any kind of flowers. I could walk down the street and find flowers that had been run over a thousand times and she would think it looked like a million dollars,” Mr. Basco said on Friday morning.

Hour later, the La Paz Faith Memorial and Spiritual Center in El Paso would be spilling over with bouquets, as hundreds of strangers came to pay their respects to Ms. Reckard at her visitation and prayer service.