The second multiple killing in less than a week has hit the normally less-violent Mexican state of Oaxaca.

The Oaxaca state prosecutor's office says a man, a woman and their son were shot to death Thursday in the southern city of Juchitan. The office says a hand-lettered sign left at the scene suggests the slayings were linked to a dispute between criminal gangs.

The killings come three days after eight adult members of a family were killed in the popular Oaxaca beach resort of Puerto Escondido. The prosecutor's office says the victims were shark fishermen and an early line of inquiry is whether they may have been involved in other activities while at sea.

Oaxaca has largely avoided the drug violence plaguing other states.