A gunman rolls up to a school in Penilee on Monday morning with the weapon concealed in a child's buggy and shoots a well-known Glasgow gangster.

At a school in Bishopbriggs 15 months earlier another high-ranking hood is shot as he picks up his daughter from primary.

And on the same day as this week's attempted murder, a High Court trial is halted because of “unsurmountable difficulties”.

These two horrific murder attempts and the failed trial are apparently unconnected.

But one theory that police investigating this latest school assassination attempt at St George's Primary will be working on is that they are the latest grisly events in a tit-for-tat war between two vicious city crime families, the Daniels and the Lyons.

Certainly all of those involved are known to each other and with a level of mutual hatred and violence which spills onto the streets.

“There's a myth that shooters are mindful of passers-by, 'civilians', but that's just like the honour among thieves. Nonsense,” said one gangland source. “You watch for patterns of behaviour so that you can work out where the best opportunity for a hit is. If it involves a school run, well that's just tough luck. Of course you don't want to hurt innocents but your first priority, along with getting the guy, is to make sure you're walking away from it.”

Ross Monaghan leaves the High Court after being acquitted of Kevin Carroll's murder in May 2012

This Lyons-Daniels enmity goes back more than two decades and has seen fatal and non-fatal shootings, vehicle hit and runs, knifings, firebomb attacks, police corruption and copious amounts of drugs, traded and consumed.

Ross Monaghan, who was shot in the back as he delivered his child to school on Monday is a major member of the Lyons gang. He has a conviction for cocaine dealing and was cleared of shooting dead Daniels' chief enforcer Kevin 'Gerbil' Carroll almost seven years ago to the day, on January 13 2010.

Carroll ran a team of thugs who staged 'alien abductions' of rival dealers, many of whom worked for the Lyons. They were so called because victims, usually found wandering in a state of semi-undress, would claim they could not remember anything afterwards. Gerbil was, by most accounts, a maniac. And incorrigible. Not a healthy - but certainly a combustible – combination.

The Gerbil was killed by masked assassins in the car park of the Robroyston Asda superstore as he sat in the back seat of his Audi. The two guns used to shoot Carroll were discovered 11 days after the killing by a team of gardeners working in the shrubbery behind Coatbridge Library. Monaghan's DNA was found on the handle of one of them. But despite this the case against him collapsed for lack of evidence.

Ross Sherlock

Police will be considering that, among other things, whoever shot Monaghan on Monday was perhaps deeming that verdict to be flawed.

Gerbil's best pal was Ross Sherlock, who lives in Bishopbriggs. In 2006 both were the victims of a drive-by shooting there, presumably by Lyons' gunmen, the Gerbil taking a bullet wound.

Three weeks later, in December, a bloodbath erupted on the forecourt of Applerow Motors in Lambhill, owned by David Lyons.

Two masked gunmen in long coats walked in and started shooting. It was over in minutes but by the end of it Lyons' 21-year-old nephew Michael was dead on the ground, his cousin Steven, a mate of Ross Monaghan's, was badly-wounded as was a third man, Paisley thug Robert 'Piggy' Pickett who, amazingly, couldn't recall the crucial events when the case came to trial.

The school attempt on Daniels' man Sherlock was either the fourth or the fifth (perhaps even he is unsure). It happened on Thursday, September 24 2015, just after 3pm at St Helen's primary in Bishopbriggs as children were filing out and parents picking them up. He was there for his.

Three shots rang out hitting Sherlock, who was wearing a bulletproof vest, in the arm and hand.

This may have been triggered (pun intended) by the allegation that he had stolen £2 million in Lyons' drug money from a house in Castlemilk.

In May last year armed police raided Sherlock's home looking for firearms, but came away empty handed. Then in October he rammed his BMW X5 car into a Vauxhall Corsa outside a football complex in Ruchazie, sending the other car back 20 metres. It is understood that he believed the other driver was a member of a rival gang out to kill him.

Police inquiries continue.