Don't listen to this advice, there is probably no one rule that can be applied to all situations involving hostile situations with weapons!!!
Occasionally we get questions on this site that ask for advice for personal situations where only a professional familiar with the exact and full details can help, those question (usually of the medical nature) get closed because they don't have an actual claim in them. In this case there is a claim and the claim will be addressed, but it's very important to emphasize
Consult only professionals regarding life and death situation, don't trust unsourced and/or anonymous posts on the internet.
end of disclaimer
After the disclaimer, as the snopes article dealing with this claim states:
We don't know the origin of the claim that someone shooting at you "will only hit you 4 in 100 times", but we're highly skeptical of the notion that a gun-wielding bad guy in relatively close proximity to a human target hits what he's aiming at only once out of 25 times (even if the target is a moving one). And just because the shooter may not hit a "vital organ" doesn't mean the victim is going to get away — a gunshot to just about any body part will usually inflict enough pain or physical damage to hamper the escape of someone fleeing on foot.
The claim's source is unknown, but it's neither a police officer nor a self defence expert.
More importantly, the hit ratio of a shooter depends on a wide variety of parameters, including the shooter's training, expertise and state of mind, the weapon they are holding, the position of the victim and other.
In several high profile cases, however, shooters got better results than 4% hit rate.
In the Virginia Tech Massacre the shooter fired at least 174 rounds and hit 47 people with at least three bullets each, rounding the number of fires shot up to 180, and taking the minimum of 3*47=141 bullets hits give us 78% hit rate.
During this second assault, he had fired at least 174 rounds, killing 30 people and wounding 17 more.1 All of the victims were shot at least three times each
In the Sandy Hook Shooting, the total number of bullets Adam Lamza shot is unclear (source: The New York Post), but according to CNN he shot
Lanza didn't make it home alive. Nor did the 26 people -- 20 of them schoolchildren ages 6 and 7 -- he shot dead in less than five minutes, firing one bullet roughly every two seconds he was at Sandy Hook Elementary School.
rounding the number to 150 rounds (5*60*1/2) and assuming that he hit each victim with only one bullet will give 17.3% hit rate or 13% if we round the number of bullets to 200.
In the 2014 the Mall in Columbia shooting the shooter shot 6-9 bullets from a 12-gauge shotgun and hit 7 people, even assuming that only 1 bullet hit all the people (some ammo for 12-gauge shotguns has a high spread) and shot 9 bullets gives 11% hit rate.
On January 25, 2014, at around 11:15 a.m., 19-year-old Darion Marcus Aguilar entered a Zumiez store on the second floor of the mall, armed with a 12-gauge shotgun, and fired six to nine shots, killing two employees—21-year-old Brianna Benlolo and 25-year-old Tyler Johnson—and injuring five others before committing suicide.
Trained police officers, in stressful situations can get to hit rates near 50%, depending on the distance, and situation:
A Hail of Bullets, a Heap of Uncertainty, The New York Times:
New York City police statistics show that simply hitting a target, let alone hitting it in a specific spot, is a difficult challenge. In 2006, in cases where police officers intentionally fired a gun at a person, they discharged 364 bullets and hit their target 103 times, for a hit rate of 28.3 percent, according to the department’s Firearms Discharge Report. The police shot and killed 13 people last year.
In 2005, officers fired 472 times in the same circumstances, hitting their mark 82 times, for a 17.4 percent hit rate. They shot and killed nine people that year.
In all shootings — including those against people, animals and in suicides and other situations — New York City officers achieved a 34 percent accuracy rate (182 out of 540), and a 43 percent accuracy rate when the target ranged from zero to six feet away. Nearly half the shots they fired last year were within that distance.
In Los Angeles, where there are far fewer shots discharged, the police fired 67 times in 2006 and had 27 hits, a 40 percent hit rate, which, while better than New York’s, still shows that they miss targets more often they hit them.
Ready, Fire, Aim: The Science Behind Police Shooting Bystanders, Times.com:
While incidents of police shooting bystanders are uncommon, they shouldn’t surprise New Yorkers (or anyone else) when they happen. Just last year, New York police injured nine onlookers in the course of responding to a murder suspect near the Empire State Building. As police chased the man through rush hour crowds, he fired at the cops; they returned 16 shots, hitting the man 10 times. That actually counted as accurate shooting for the NYPD.
According to a 2008 RAND Corporation study evaluating the New York Police Department’s firearm training, between 1998 and 2006, the average hit rate during gunfights was just 18 percent. When suspects did not return fire, police officers hit their targets 30 percent of the time.
All emphases are mine
A wide variety of factors affect the hit ratio of an assailant, and in many cases, hit ratio is high, even though those are stressful situations where the targets were probably moving or hiding, there is probably no way to know if an anonymous assailant is an ex navy seal with 100% hit rate, or doesn't know how to properly handle their weapon.
My anonymous and unsourced advice would be to try to avoid the attacker using their weapon, but see disclaimer above.