Six men have been shot dead and another 10 injured during a football training session in the Brazilian city of Manaus, wrote dailymail.co.uk.
The gunmen slaughtered their victims after separating the adults from children who were in the area when the killers arrived.
All but one of the murdered, who included a 17-year-old, played for an amateur side called T5 Jamaica.Local TV stations broadcast graphic images of the dead men lying in pools of blood on and near the dirt pitch where they were targeted.
Loved ones were seen burying their heads in their hands and crying as they stooped down beside them.
They also showed images of one injured player filmed hopping into hospital in agony after being shot in the leg - and blood on the pitch and patches of grass beside it after a botched clean-up.
The dead men have been named locally as Michael de Sena Passos, 33; David Costa da Silva, 27; Ronaldo Oliveira de Souza, 23; Edilson Xavier Diniz Junior, 24; Jose Diego Sena Serrao, 17; and Rodrigo de Oliveira Souza, 24.
Local reports said the eldest man killed had a drugs conviction and police are said to be linking the massacre to a drugs feud between two of Brazil's most violent criminal gangs.
One of the nine injured people, a 16-year-old boy, is said to be in a 'critical condition' in hospital.
The surprise ambush happened on Tuesday night in a neighbourhood of Manaus called Compensa.
It is birthplace of the so-called Family of the North drug gang responsible for New Year massacres in two jails in Manaus in which 63 prisoners were butchered.
The victims of the prison massacres were mainly from the rival Sao-Paulo based drugs gang First Capital Command (PCC).
Police are understood to be concentrating on the theory Tuesday night's massacre was the work of the PCC, although they have not ruled out Family of the North in-fighting.
Three of the getaway cars used by the killers have already been discovered.
Regional Public Security Minister Bosco Saraiva said: 'Everything is pointing to the deaths being the result of a war between rival drugs gang who were disputing control of the area.'
Witnesses have told police the killers were dressed in black and were heavily armed with weapons including rifles and pistols and covered their faces with masks as they got out of their vehicles.
Some of the victims were shot by gunmen waiting outside the exit to the fenced-off pitch as they tried to run for safety when they started to come under fire.