The suspected gunman was identified as 42-year-old Lawrence Jones, a parolee who had worked for the company for 14 months. Police do not know what prompted the attack.
Investigators say Jones got to work at 5 a.m. About three and a half hours later, he shot four victims with a .357-caliber handgun. He tried to shoot another person but was reportedly out of bullets. Police say Jones then walked outside, reloaded his gun and shot himself. He died later at a hospital.
There were about 65 people at the the workplace when the shooting began. About 30 employees witnessed the shootings, according to police.
Salvador Diaz, 32, was pronounced dead at the scene, and Manuel Verdin, 34, died later at a hospital. Arnulfo Conrriguez, 28, was in critical condition. Fatima Lopez was expected to be released later from a hospital, police said.
Fresno Police Chief Jerry Dyer said in a Tuesday news conference: "We know that [Jones] has an extensive criminal history that dates way back into the '90s. To our knowledge, he is a discharged parolee. ... We have secured his residence here in Fresno. We are looking to ensure that there were no other victims."
KABC's sister station, KFSN, in Fresno reports that the suspect, Lawrence Jones, had four prior felony strike convictions. His last was in 2002 when he led police on a chase in a stolen car. He injured a family of four in that incident.
At that time, Jones was diagnosed with "intermittent explosive disorder" and was sentenced to 10 years and 8 months in prison. During sentencing, the judge struck two of his prior strikes, making him ineligible for a life sentence under California's Three Strikes law.
The Associated Press and KFSN contributed to this report.