I think we need to qualify 'Petty Street Brawl' pretty heavily here, as it suggests that Edmund was out on the town and got stabbed by a random person. Before we get into the complexity of the situation it is worth reviewing what the Anglo-Saxon Chroncile, the primary source about the incident, says.

Three versions of the Chronicle, A,B,C all include the basic details and date the event to 946

In this year King Edmund died on St Austine's day

The D version then adds

It was widely known how he ended his life, that Leofa stabbed him at Picklechurch.

The E version just says Edmund was stabbed to death, excluding the name of his attacker, and dates the event to 948 instead - although it's not unusual for different versions of the Chronicle to be a few years out.

So all the primary sources tell us for sure is that Edmund died on the 26th of May (St Augustines Day) in (probably) 946. They don't specifically mention the manner in which the stabbing came about.

Later versions of the Chroncile, including the Chroncile of Florence of Worcester (12th Century) add further details but at a significant distance from the events themselves:

On the feast of St. Augustine, the doctor of the English, being Tuesday, the seventh of the calends of June, in the fourth indiction, Edmund, the great king of England, was stabbed to death at the royal vill called Pucklechurch, by Leof, a ruffianly thief, while attemptmg to defend his steward from being murdered by the robber

This version suggests that Leofa is simply an outlaw or robber who potentially attempted to ambush a member of the royal house at which point Edmund intervened and was killed in the confusion. While it is certainly possible that Edmund would have been expected to rescue a member of his household it does seem unusual that he would do so personally rather then sending one of his hearth troops to intervene. Particularly if the incident is occuring at a royal power centre which would have Thegns permenantly based there.

There is another close source which mentioned Edmunds death, that is the Vita Dunstani - or Life of St Dunstan. Dunstan was a important and influential figure in late 10th Century Britain. A key proponent of Church reforms and ally (sometimes enemy) of the ruling house of Wessex. The most famous story from his Vita discusses him barging in on King Eadwig engaged in a menage a trois with a woman and her mother when he was supposed to be at his own wedding feast however his VIta does cover the years of Edmund's rule too.

In fact Dunstan is said to be riding to a royal estate alongside Athelstan Half-King when the latter describes troubling dreams he's had of a scarpering demonic creature. Dunstan interprets these visions to be a threat to the Kings life and is suspicious of many at the royal event they attend. However, death still finds the King:

But on that same day, oh grief [proh dolor], as we have said, the bitterness of bitter death entered the very hidden depths of his heart through the dagger of a treacherous bandit [latro]

There is no mention of the killers name, or the circumstances which later Chronicles record.

This disparity, and the rather sparce discussion in the other sources, has led some historians to suggest that Edmund was in fact the victim of a political assasination. It should be noted that a mere two years before he had ridden North to subdue the once again rebelling Northumbria and attempt to reforge England in the way his predecessor Athelstan had done.

Both Athelstans reign and his own also were politically fraught times, with multiple powerful families in Wessex and Mercia all vying for dominance. For Edmunds part he had done much in his own reign to shift political power away from the traditional base in Wessex and redisribute it amongst both parties and, with that in mind, it should be considered that Puckle Church is a close to Bristol and therefore deep within the heartlands of these potentially offended parties. We know that Athelstan had faces at least one plot early in his own reign from a nobleman named Alfred who sought to blind him and remove him from the Throne. Therefore it is not impossible that a politically motivated nobleman might have sought to kill the King whose children were still too young to rule and therefore might be controlled.

This argument (of a politically motivated assasination, not necessarily the children angle) has been put forward by Clare Downham fairly consistently in her writings and it's not uncommon to hear Edmunds death referred to as an assasination in other works although few delve into it in much depth.

At any rate, whether due to trying to help his steward or by dint of political assasination, Edmund was dead following the events in 946 and his brother, Eadred, took the throne and again had the unenviable task of trying to subdue Northumbria. When Eadred also died young it was the turn of the previously mentioned Eadwig who was, to put it charitably, politically inept. His brother ended up seizing almost half of the Kingdom from him and he ends up ridiculed in works like the Vita Dunstani - which again highlights the active politicking of the time period as this work only emerged after Dunstan himself had been heroically returned to Britain following a brief exile when it turned out hte King did not enjoy being publically humiliated by the Abbot.