Bhishma Rests On the Bed of Arrows : Episode 141

The tenth day war commences. Krishna steers the chariot to where Bhishma is. Bhishma picks up his bow to shoot at Arjuna, but retracts when he sees Shikhandi. At first, Shikhandi shoots darts at Bhishma, but they are not powerful enough to pierce him fully. Bhishma drops away the bow and arrow, saying he would not lift any weapons in the presence of women. After Shikhandi fires a volley of arrows in full display of his hatred for Bhishma, he hands over the weapons to Arjuna. Arjuna now begins a fierce battle in which he shoots a barrage of missiles that pierce his body, without leaving even an inch uncovered by the shafts.

Bhishma groans in pain, gets down the chariot and totters about on the ground.

The soldiers from both sides of the battle stop fighting and watch this spectacle in awe. With tears in his eyes, Arjuna continues his assault. Duryodhana and Dushasana are totally shaken, Only Shakuni watches the scene, fully elated that his long cherished and most anticipated event has finally happened. He recalls with glee the promise he makes to his father about causing Bhishma's death as a retribution for their being starved to death in captivity. The celestials shower flowers over Bhishma.

The darts have covered Bhishma fully on all sides and have made a bed to rest upon. Bhishma expressess happiness at being assailed by none other than his own beloved Arjuna.

He asks him to make a pillow of arrows to rest his dangling head. He then asks for Ganga water, and Arjuna complies by sending a fountain of water to gush from the earth into his thirsty mouth to resuscitate him.

Sanjaya weeps as he narrates the scene to Dhritarashtra and Gandhari. Everybdoy is plunged in grief.

Is Krishna's act in scripting Bhishma's end in accordance with Dharma? Here's an article in Tamil for your reference.
https://mahabharatham.arasan.info/2014/09/are--deeds-of-Krishnaconspiracy-or-virtue.html