Four people are killed and 15 are injured as three shootings erupt in Dallas's Deep Ellum district on Halloween night

Police Chief Daniel Comeaux confirmed at least one suspect was in custody but said detectives were still working to establish whether the three incidents were connected.

The deadliest single shooting killed three people on Commerce Street near South Crowdus Street; a fourth victim died in a third shooting on the 2600 block of Elm Street.

Five of the 15 injured were bystanders with no involvement in the shootings, police said, all transported to nearby hospitals.

'This is a really big scene — it's spread out,' Comeaux said, as officers from across the city were deployed and multiple blocks shut down.