The incident that has been reported to the police watchdog the Directorate of Professional Standards.
In a statement the police said: "Police carried out a proactive, intelligence led operation at the A10, near the junction with Richmond Road, Dalston at approx 1650hrs on Friday, 22 June.
"A male suspect was detained - taser was discharged. This caused a facial injury and the male was taken to a London hospital as a precautionary measure.
"The Directorate of Professional Standards has been informed as is standard procedure.
"The male was arrested in connection with an ongoing murder investigation."
The suspect was Dwayne Fulgence (28) of no fixed abode, charged with the murder of Marlon Campbell, 23, on 16 June 2012 in Bellingham SE6. Details of the charges can be found here which include the possession of a firearm and the intent to endanger life. Apparently four other people were arrested too.
Kingsland Road was closed for a while. I imagine to gather evidence to explain whatever it was that happened. I was passing by on my bike and took a picture. (The last incident I saw at this junction).