"An argument over a dog, and a lie of someone pulling a gun on someone,” she said when describing the moments before shots were fired.
Alonzo reportedly was shot in the head.
Sims said her family has helped take care of the neighborhood dog in the past, but tempers flared when the dog began barking at others, including family members.
WHBQ's Jeremy Pierre counted more than 20 bullet holes in the front of the family's home. Some of the bullets shattered glass and hit other victims.
Blytheville police said two teens were also shot.
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"It's just hitting us hard because I just lost my daughter in April to a murder, and I just lost my son in the same way," Sims told WHBQ.
Alonzo and the two teens were airlifted to Regional One Hospital. Alonzo later died.
Investigators told WHBQ that 35-year-old Antonio Harris died on the scene after he was run over by a truck.
People who witnessed the incident said he attempted to de-escalate the situation before the shooting started.
"The people that did this (are) still walking around here, and something needs to be done,” Sims said.
Investigators told WHBQ that they are depending on surveillance footage from the home to help them arrest suspects. One person is in custody.