As per the post mortem report, Joseph's broken neck bone pierced into his lungs, resulting in the death.
'As consolation, I am taking a pair of clothes with me,' read the note, which went viral on social media.
The number of thieves involved in the incident are not known at present, police said and added that they were going through CCTV footage from the area to identify the culprits.
They were held on the charge of stealing 20 sovereigns of gold, cash worth Rs 3,25,000 and other valuables worth Rs 25 lakh.
Footage from the bus shows how a fellow traveller lifted Rs 25,000 from a woman's handbag at Ottapalam.
Mohammad Firoz, who is accused of murdering and burying his friend Muhammed Ashique, 24, at Palappuram in Ottapalam, made calculated moves to avoid raising any suspicions.
Assistant Police Sub Inspector Girish Kumar of the Elamakkara Police station was stabbed by the thief near Kochi's Edappally Metro Station
Police identified the arrested men as Orrakam panchayat member N T Shibu, 31, of Vengara, Mahit, 34, of Manjeri, Krishnaraj, 28, of Kavanoor, and Saseedharan, 32, of Kottakkal.
The police have arrested three youths over a chain-snatching case.
The victims include a mother and daughter who have claimed to have lost 35 sovereigns of gold ornaments and two mobile phones.