A team of Thumba Police arrested the fugitive on Thursday morning.
The deceased was identified as Shishir.
The murder happened during a rape bid at noon on August 13. Jalaja's husband was abroad and her children were based in Bengaluru then.
The accused had taken his wife to the hospital with injuries to her head and other areas. He had claimed that she suffered the injuries following a fall from a chair.
The accused, Jayan, told the police he wanted to avenge the killing of his wife, for which the deceased's son is jailed.
Palarivattom-native Ullash Hariharan and his daugther, Krishapriya and son, Ekanath were the deceased.
The sheriff's office didn't identify those killed or give details about what led to the shooting.
It is suspected that an altercation during a drinking session led to the murder.
The Uttrakhand and Punjab Police in a joint raid, have detained a man in Dehradun, who is said to be involved in the killing.
His father also demanded that the Punjab government involves the CBI and the NIA in the inquiry.