The 44-year-old grandfather was shot at around 7.05pm on Thursday, August 26 in Westray Street.
He died in hospital two days later.
In a statement issued on Wednesday, his brother, Andrew McGregor, said: "I am absolutely shocked and devastated at the loss of my brother John in such horrific circumstances.
“He was a loving father, granda, son, brother and uncle and will be sorely missed by all of his family and friends.”
He added: “On behalf of my family I would like to thank the members of the public who tended to John and provided first-aid on Thursday evening and the NHS staff who tried to save John's life.”
It comes as Police Scotland's Major Investigations Team issued an appeal for information relating to a white Vauxhal Corsa van that is believed to be connected to the murder case.
Detective Superintendent Raymond Brown, senior investigating officer, said: “Our enquiries are continuing into the murder of John McGregor and I am again appealing to anyone who may have information to speak to police.
“I am particularly keen to hear from members of the local community who may have vital details surrounding the circumstances of the incident and could help trace those responsible.
“If you were in the area of Westray Street at the time of the incident or have any information surrounding a white Vauxhall Corsa van that was found on fire on Etive Crescent, Cumbernauld around 9.50pm on the same day, please come forward and speak to officers."
Detectives have set up an online portal to encourage members of the public to submit information.
The Major Incident Public Portal (MIPP) is a website that gives the public access to a form so they can send information directly to the major incident teams based at the Scottish Crime Campus and can be accessed here.
Police can also be contacted by calling 101 and quoting incident number 3276 of Thursday, August 26, 2021.
Alternatively, Crimestoppers can be contacted anonymously on 0800 555 111.